In a Y bar for forming coupling elements, an opening angle of a pair of right and left leg parts is narrower than that of the ordinary ones. The strain sensor includes at least one microstructural beam member anchored to a substrate at one position and having a portion which is freed from the substrate during formation to displace as a result of the strain in the beam member. The cover is formed with a coupling portion on one side thereof. An array of local crystal modifications is formed in the first Group IV semiconductor in accordance with the pattern.